A growing number of potential native and engineered biothreat agents effectively limit the proactive protection of public health through vaccination. An alternative approach relies on the use of corresponding protective antibodies that are pre-made and are used as injectable drugs in reactive rather than proactive mode. The implementation of this approach, however, is complicated by the fact that administration of non-human antibodies can trigger development of adverse reactions. Securing of human antibodies in sufficient quantities so far has been a challenging task. Also, the traditional approach of producing antibodies depends on the existence of corresponding vaccines and cannot be used for expedient development of protective agents against newly emerging infections. To overcome these hurdles we propose to develop a novel system for assembly and production of human/human chimeric antibodies. Such antibodies can be generated at a fraction of the cost of raising polyclonal antibodies and in substantially shorter times than traditional monoclonal antibodies while still remaining human in nature. In general, our system will be much safer to operate with than hybridoma technology. In addition, it can be used for development of protective entities at the first signs of emergence of new threat agents. Phase I efforts will test the feasibility of our approach by developing human/human chimeras that will recognize botulinum neurotoxin serotype A. To assemble such chimeras, we will introduce a proprietary cloning scheme that reduces the risk of modifying native antigen-recognizing sequences and substantially simplifies the process of assembly of immunoglobulin-encoding sequences. This will make the system suitable for high-throughput format applications. Regulatory elements incorporated into cloning vectors will enable rapid detection of cells producing antibodies of interest and selection of host cells for industrial production, thus increasing the efficiency of the process and decreasing price of the final product. During Phase II, the developed cloning approach and expression vectors will be used to generate IgG variants of chimeric antibodies that will be able to neutralize toxic effects of botulinum neurotoxin serotypes A and B and will be suitable for use as anti-botulinum drugs. The developed enabling technology will be suitable for generating protective antibodies against other biothreat agents. PUBLIC HEALTH RELEVANCE: The current project will provide a new way for development of human anti-pathogen antibodies and opens new opportunities for passive vaccination as a way of protecting humans against infectious diseases and toxins.